Effect of Mechanical Alloying and Trace Y2O3 Addition on Microstructure of Fine-Grain Tungsten Heavy Alloy Rods

Fine-grained 93W-4.9Ni-2.1Fe tungsten heavy alloy rods with diameter of 25 mm were fabricated by mechanical alloying (MA), trace Y2O3 adding, cold isostatic pressing and sintering. The tungsten grain size of the as-sintered alloy was 3-4 mu m. The effects of MA, addition of trace Y2O3 and sintering process on the densification and microstructure of the alloy were studied. It is indicated that the tungsten grains were spheroidized during liquid phase sintering at 1480 degrees C, and at this temperature the sintering time greatly affects the control of tungsten grains growth. The grain size of the tungsten alloy sintered at 1480 degrees C for 30 min was 5-8 mu m. The grain size of the tungsten alloy was 8-10 mu m when the sintering time was 60 min at 1480 degrees C. The addition of trace Y2O3 further prevents the tungsten grain growth, effectively refining the tungsten grain and inducing a homogeneous microstructure. The tungsten grain size of tungsten alloy sintered at 1480 degrees C for 60 min with addition of Y2O3 was 3-4 mu m and more uniform.